Gas fired oil-well burner



Aug. 21., 1962 J. O. SCOTT GAS FIRED OIL-WELL BURNER Filed 001:. 7, 1958 INVENTOR I 0. Scott 3,050,123 GAS FIRED OIL-WELL BURNER J. 0. Scott, Tulsa, Okla, assignor to Cities Service Research and Development Company, New York, N.Y., a corporation of New Jersey Filed Oct. 7, 1958, Ser. No. 765,893 9 Claims. (Cl. 16659) This invention relates to an oil-well heater, and more particularly, to an improved gas fired burner particularly adapted for initiating combustion in thermal recovery processes.

It is widely recognized in the oil production industry that considerable portions of oil present in the formation are not recoverable by natural depletion processes. This condition may be due to several factors which include loss of natural gas drive, clogging of the formations due to the presence of insoluble materials, greater average viscosity of reservoir oil after recovery of the less viscous oil and deposition or build-up of insoluble materials at the well bore which prevent free flow of oil from the reservoir to the recovery well.

A variety of methods have been used to improve recovery of oil from reservoirs after initial natural drives have become exhausted. These methods are generally referred to as secondary recovery methods and include such techniques as water-flood, gas driving and thermal oil displacement. It is with the latter technique in which an underground heat wave is propagated that this invention is particularly concerned.

In the thermal recovery technique, combustion is initiated by means of a burner positioned in the borehole adjacent to a zone in which heat is to be generated to provide a means for simultaneously lowering the viscosity of the oil present and generating gases which will assist in driving residual oil to a producing well.

To initiate combustion, both electrical and gas fired heaters have been used. The electric heaters have very serious limitations in that they require large electric cables to supply current to great depths and are expensive to construct and operate. Similarly, gas fired borehole heaters previously utilized have been of complex design which necessitated separate and concise control over the quantities of gases and air injected to obtain a combustible mixture, have had limited burner surface area and were often extremely hazardous to operate because of the possible existence of a combustible mixture in the borehole which would explode when ignition of the burner was attempted. Typical of burners of this type is that disclosed in US. 2,584,606, which is limited in its application by requiring separate tubes for air and combustion gas, close metering of the gases diflioultly obtained by utilizing a valve such as shown at 24 which at extreme depths presents a very serious limitation on the effectiveness of the burners operability.

The improved gas fired oil-well burner of the present invention overcomes the limitations and disadvantages of existing equipment by providing an extremely effective explosion-proof burner which is inexpensive to fabricate, easy to operate, adapted to provide an even distribution of generated heat over a wide producing formation front, readily adapted to be used at any depth and automatically regulating the mixture of combustible gas and combustion supporting gas to provide an intense burning pattern Without the necessity of providing separate conduits to deliver the combustion gas and combustion supporting gases to the burner.

These and other advantages can be obtained from the new and improved gas fired burner of the present invention. The burner of the present invention is adapted to be lowered into the well through the well tubing and to be seated at the lower end thereof in that portion of the 3,,l23 Patented Aug. 21, 1962 uncased borehole in which the initiation of combustion is desired. The burner includes a gas intake chamber tapered at its lower end to provide a gas tight fit with the swaged end of the well tubing. The gas tight fit is provided by means of a seal carried in the tapered end of the gas intake chamber. In the bottom of the gas intake chamber, a nozzle is provided which extends below the end of the well tubing and delivers combustion gas to an ejector positioned below the nozzle. The ejector is sup ported by arms fixed to the gas intake chamber. An elongated perforated burner tube is fixed to the lower end of the ejector and receives a combustible gas mixture from the ejector. An ignitor is exteriorly positioned on the lower end of the ejector to initiate combustion of the gas mixture as it escapes from the perforations in the burner tube. Combustion gas delivered to the well tubing fiows into the gas intake chamber through a plurality of ports and is delivered by the nozzle to a mixing zone in the upper end of the ejector. Air introduced into the annulus between the borehole and the well tubing enters the air intake zone at the nozzle where it is entrained or accelerated into the mixing section of the ejector and through an area of reduced cross section from whence the mixture of gas and air expands into the diffusing section of the ejector and into the burner tube. Maintaining the volume ratio of injected air to injected gas above about 20 to 50 avoids the danger of explosion since the ejector entrains with proper positioning and sizing of the nozzle only as much air as is needed to form the combustible gas mixture.

A more complete understanding of the improved burner of the present invention can be seen from the description and attached drawings in which:

FIGURE 1 shows an enlarged view partly in section of the burner as it would be positioned in a borehole to initiate combustion.

FIGURE 2 is an enlarged view in section of the gas intake and mixing sections of the burner.

FIGURE 3 shows an enlarged view of one form of ignitor suitable for use on the improved burner.

FIGURE 4 shows an alternate embodiment of the gas intake chamber seat and seal.

FIGURE 5 shows another embodiment of the gas intake chamber seat and seal structure.

FIGURE 6 shows a perforated bafile tube.

Referring now to FIGURE 1, the burner assembled for use is shown. The burner, generally identified by numeral 1, includes the gas intakechamber 2, provided with a plurality of intake ports 3, a nozzle 10, supports 8, ejector 2t), ignitor 30 and perforated burner tube 40. A weight or sinker bar 50 attached to the top of the gas intake chamber includes a cable clamp and fishing head 52 to fasten the burner to the lift and conductor wire line identified as 54.

In FIGURE 2 an enlarged view of the body section of the burner is shown. As indicated, the body section includes gas intake chamber 2 which is closed at both ends and includes a plurality of gas intake ports 3. Cham ber 2 has a diameter less than the inside diameter of well tubing 14 and is tapered at the lower end 5 to insure a gas tight fit with the swaged end 12 of tubing 14. Seal means, such as an O-ring 6, are provided on tapered end 5 to insure a gas tight fit with the swaged end when the burner is positioned in the tube. A single bore nozzle 10 is centrally positioned in the bottom of chamber 2 and communicates by way of tubing 11 with the interior of the chamber to receive combustion gas introduced at the surface and delivered down the annulus 9. Nozzle 10 is fixed to chamber 2 by fitting 17 which is designed to permit vertical adjustment of nozzle 10. As shown,

.nozzle 10 extends below the end 13 of tubing 14. Fastened to the lower end of chamber 2 is a plurality of support arms 8, These support arms may be threaded into the base of chamber 2 as shown or fixed to the exterior surface thereof as by Welding or other means. Arms 8 are of sufiicient length to provide support for the ejector tube When an electrical ignitor is utilized as hereafter described, arms 8 may be hollow to provide a conduit for the wires delivering electricity to the ignitor. As shown, the side walls of ejector 20 may be grooved to receive support arms 8. Ejector 20 is fastened to tubes 8 by bolts, welding or other means as desired. Ejector 20 includes a mixing zone 21 and a dilfusion zone 22. The middle portion 23 is of smaller diameter than zones 21 or 22 so as to obtain a venturi eifect in the ejector when combustion gas from nozzle and air delivered from the annulus 16 is mixed in zone 21.

Fastened to the lower end of ejector is the perforated burner tube 40. Tube 40 is fastened to the lower end of ejector 20 by means of threads 24 or other suitable means such as Welding or the like. Tube 40 is closed at the lower end 41 and is provided with a plurality of perforations 42. Proper selection of the number, size and distribution of holes 42 along tube 40 provides a constant rate of heat output per unit length of tube. Tube 40 may be of any length provided holes 42 are distributed properly to permit gas flow along the full length of the tube by increasing the number of perforations 42 per unit length as the closed end 41 is approached. The combustible gas mixture can be ignited at one or several points on the tube and the flame will travel the full length of the tube and ignite the gas leaving each perforation. If the perforations are of about /s inch or less in diamter, the combustible gas mixture will burn only on the outside of tube 40 and will not flash back into the tube.

To avoid undesirable blowout or distortion of the flame pattern around tube 40, particularly in the vicinity of the upper end, near delivery of combustion supporting air, the perforated bafiie tube 44 may be placed around tube 40. The battle tube will have a diameter slightly larger than the diameter of tube 40 and a length substantially'coextensive with tube 40. The baflle tube may be of shorter length if a satisfactory flame pattern is obtainable along the length of tube 40. The baflle tube is, of course, perforated in a manner similar to that of tube '40 so as to provide an even and balanced flame pattern throughout the length of the burner tube.

To obtain ignition of the combustible gas mixture, an ignitor is provided on the exterior of burner tube 40. Ignitor 30 may be of any suitable type, such as a spark device or chemical ignitor such as burning phosphorus or magnesium. A convenient type of heating coil igniter is shown in FIGURE 3. This ignitor includes a small gage resistance wire coil 36 insulated from the burner tube and fastened to the burner tube by clamps or other suitable means. Conductors 31 and 32, insulated by porcelain insulators 33, deliver current to coil 36. Coil 36 is exposed fully or in part to gas issuing from burner ports. If conductors 31 and 32 are different metals, their junction at 34 will provide a thermocouple. When a flame is produced in the vicinity, the thermocouple 34 will generate a potential difference which can be detected by a potentiometer at the surface. This is accomplished by connecting wires 31 and 32 to the potentiometer after delivery of current by them to the ignitor 30 has been continued for a sufiicient time to allow the combustible gas to ignite. To protect ignitor 30 an ignitor shield 35 is positioned on tube below the ignitor 30. If desired, more than one ignitor may be positioned on tube 40. In such event the ignitors of either chemical or electrical type are spaced exteriorly on tube 40 at intervals to insure balanced ignition throughout the length of tube 40.

When it is desired to initiate combustion across an oil bearing formation 15, the burner is lowered into the well tubing to a point where the tapered end 5 of chamber 2 contacts the swaged end portion 12 of tube 14. This swaged end may be added to the well tubing by means of a coupling or the lower end of the last length of tubing may be fashioned into the swaged nipple as desired. The seal 6 insures agas tight fit between the swaged end 12 and the gas intake chamber 2. Combustible gas which may be a suitable combustible material such as natural gas, methane, ethane, propane, butane, or various combinations of these is delivered down the tubing and enters ports 3 into chamber 2. Gas, so delivered, leaves the nozzle 10 and entrains air which has been injected down the annulus 16. Gas from the nozzledraws air into the mixing section of ejector 20, through the reduced area section 23 and into the diffusing section 22, wherein the pressure increases to a level slightly above the pressure of the air in the annular space 16. If the ratio of injected air to injected gas is kept above about 20:1 to 50:1 depending on type of gas, no danger of explosion will exist.

In FIGURE 4 and 5 additional embodiments of the gas intake chamber support and seal means are shown. In FIGURE 4 intake chamber 52 is supported on the shoulder of landing nipple 55 by means of the lugs or supports 56. As shown, nipple 55 is positioned on the lower end of tube 54 by means of coupling 53. A seal 58 which may be a conventional O-ring as other suitable packing means is provided on the lower end of chamber 52 to insure delivery of combustible gas to nozzle 10 as shown in FIGURE 2.

In FIGURE 5 an alternate embodiment of the gas intake chamber seat and seal is shown. This embodiment includes a shoulder 57 in the lower end of 55. The gas intake chamber 52 is tapered inwardly at its lower end as shown at 59 to seat firmly against the tapered shoulder 57. Seal means 53' are provided to insure a gas tight fit for chamber 52' in the nipple 55'.

A typical burner tube designed to operate through 2 inch tubing would have an outside diameter of 1 inch with the dimension of the combined ejector and tubular supports being slightly less than 1 /2 inches. The single bore nozzle diameter was 10, inch, the mixing section of the ejector was inch at the entry end and converged to /2 inch over a 1 inch length. The venturi throat 20 was /2 inch long and /2 inch in diameter. The diifusion section of the ejector diverged inch over a length of 2 /2 inches. With air intake at atmospheric pressure, and combustion gas being delivered to the nozzle at 23 p.s.i.g., the discharge pressure was about 002 psig, at a gas mixture rate of about 500 s.c.f.h. This gas flowed uniformly from the burner tube at a minimum velocity from each A inch port along a 15 foot burner tube in which the perforations range from 15 holes per foot in the vicinity of the ejector to 60 holes per foot at the closed end of the tube, with a total of 445 holes present. The ignitor used consisted of 2 feet of 26 gage Nichrome wire wound in a tight coil and placed in a circular grooved ceramic ring slightly less than 1 /2 inches in diameter. Electricity is furnished to the ignitor coil through an armored electric cable which is attached to a 14 gage Nichrome and a 14 gage constantan wire. A current of 4 amp. passed through the coil was suflicient to ignite the gas leaving the burner tube perforations. The junction of these wires forms a thermocouple which on increase of temperature due to the presence of a burner flame would produce a measurable potential diiference, registrable on a potentiometer connected to the armored cable. After initiation of combustion using natural gas at a rate of 36 s.c.f.h., the 15 foot burner will heat the well bore to 500 F. in about 24 hours.

As will be readily understood from the foregoing description, the new and improved burner provides a means for establishing a combustion zone over a comparatively wide depth interval in a very simple manner without the hazards of explosion and the requirements of concise control as required in conventional equipment used for this purpose.

While the burner has been described as being particularly suitable for initiating combustion in thermal recovery processes, the ease with which it may be assembled, positioned and operated makes it suitable for borehole cleaning, increasing oil flow to a producing well and freeing adjacent strata of heavy viscous materials 1mpeding oil flow to a producing well.

While this invention has been described with respect to one embodiment, it is to be understood that the invention is to be limited in scope only by the claims appended hereto.

I claim:

1. A bottom hole burner for initiating combustion in subterranean passages which includes a gas intake chamber closed at the upper end, lifting means fixed to the upper end of said chamber to permit raising and lowering of the burner in well tubing, the lower end of said intake chamber adapted to seat in the end of the well tubing, seal means associated with said lower end to provide a gas tight fit between the lower end of said chamber and the well tubing end, gas intake ports in the said chamber to receive combustion gas delivered down the Well tubing, a nozzle in the bottom of said chamber communicating with the interior of said chamber to receive combustion gas from said chamber, said nozzle having a sufficient length to extend below the lower end of the well tubing when the burner is positioned therein, a plurality of support arms fixed to the lower end of said chamber, an open ended ejector positioned below said nozzle supported by said arms adapted to receive air from the annulus between the well bore and well tubing, an elongated perforated burner tube fixed to the lower end of said ejector, said burner tube being closed at the lower end, and having an ignitor exteriorly positioned thereon.

2. A bottom hole burner for initiating combustion in subterranean formations which includes a gas intake chamber closed at the upper end, lifting means fixed to the upper end of said chamber to permit raising and lowering of the burner in well tubing, the lower end of said intake chamber being adapted to a seat on the end of the well tubing, seal means associated with said lower end to provide a gas tight fit between the lower end of said chamber and the well tubing end, gas intake ports in the said chamber to receive combustion gas delivered down the well tubing, a centrally located single bore nozzle in the bottom of said chamber communicating with the interior of said chamber to receive combustion gas from said chamber, said nozzle having a sufficient length to extend below the lower end of the well tubing when the burner is positioned therein, a plurality of support arms fixed to the lower end of said chamber, an open ended ejector positioned below said nozzle supported by said arms adapted to receive air from the annulus between the well bore and tubing, an elongated perforated burner tube fixed to the lower end of said ejector, said burner tube being closed at the lower end, and having an ignitor exteriorly positioned thereon.

3. A bottom hole burner for initiating combustion in subterranean formations which includes a gas intake chamber closed at the upper end and having closure means at the lower end, intake ports in the said chamber to receive combustion gas delivered down the well tubing, weighting means fixed to the top of said chamber, cable clamp means associated with said weighting means, the lower end of said chamber adapted to fit a seat in the end of the well tubing, said lower end including seal means to provide a gas tight fit between the intake chamber and the well tubing end, a centrally located vertically adjustable single bore nozzle in the closure means of said chamber communicating with the interior of said chamber through said closure means, said nozzle having a sufiicient length to extend below the seat on the end of the well tubing when the burner is positioned therein, a plurality of support arms fixed to the lower end of said chamber, an open ended ejector positioned below and adjacent to said nozzle supported by said arms adapted to receive air delivered down the annulus between the well bore and well tubing and gas issuing from said nozzle, an elongated perforated burner tube open at its upper end fixed to the lower end of said ejector and in fluid tight communication therewith, said burner tube being closed at the lower end and having an ignitor exteriorly positioned thereon.

4. A bottom hole burner for initiating combustion in subterranean formations which includes a gas intake chamber closed at the upper end and having closure means at the lower end, lifting means fixed to the upper end of said chamber to permit raising and lowering of the burner in well tubing, the lower end of said intake chamber being adapted to fit in the end of the well tubing, seal means associated with said lower end to provide a gas tight fit between the said lower end of said chamber and the well tubing end, gas intake ports in the said chamber adapted to receive combustion gas from the well tubing, a centrally located adjustable single bore nozzle in the closure means of said chamber extending through said closure means, said nozzle having sufficient length to extend slightly below the end of the well tubing when the burner is positioned therein, a plurality of support arms permanently fixed to the lower end of said chamber, said arms extending along the axis of the nozzle, an open ended ejector supported by said arms and positioned below and adjacent to said nozzle, said ejector adapted to receive air delivered down the annulus between the bore hole and well tubing and gas issuing from said nozzle, an elongated perforated burner tube fixed to the lower end of said ejector in fluid tight communication therewith, said burner tube being open at its upper end and closed at its lower end, and having an electric ignitor exteriorly positioned thereon.

5. A bottom hole burner for initiating combustion in subterranean formations which comprises a gas intake chamber closed at the upper end, the upper end of said chamber including means for raising and lowering said chamber in well tubing, said lower end of the chamber being shaped to fit a seat shaped in the lower end of the well tubing, said shaped chamber end including seal means to prevent combustible gas flow out of the end of the well tubing, a plurality of gas entry ports in said chamber adapted to receive combustion gas from the well tubing, a vertically adjustable single bore nozzle in the bottom of said chamber communicating with the interior of said chamber, a plurality of support arms fixed to the lower end of said chamber, an ejector supported bysaid arms below the nozzle adapted to receive air from the annulus between the well bore and well tubing, an elongated burner tube fixed to the lower end of said ejector, said burner tube being closed at the lower end and having a plurality of perforations throughout its length, said perforations increasing in number per unit length as the lower end of the burner tube is approached, and having an insulated electric ignitor exteriorly positioned thereon.

6. A bottom hole burner for initiating combustion in subterranean formations which comprises a gas intake chamber closed at the upper end, and having closure means at the lower end, the upper end of said chamber including means for raising and lowering said chamber in well tubing, said lower end of the chamber adapted to fit in a sealed relationship with the lower end of the well tubing, seal means associated with said chamber lower end to prevent combustible gas flow out of the end of the well tubing, a plurality of gas entry ports in said chamber adapted to receive combustion gas delivered down the well tubing, a vertically adjustable single bore nozzle in the closure means of said chamber communicating with the interior of said chamber through said closure means, a plurality of support arms fixed to the lower end of said chamber, an ejector supported by said arms below and adjacent to the nozzle adapted to receive air delivered down the well annulus and gas issuing from said nozzle, an elongated burner tube permanently fastened to the lower end of said ejector in fluid tight communication therewith, said burner tube being open at the upper end and closed at the lower end and having a plurality of perforations throughout its length, said perforations increasing in number per unit length as the closed end of the tube is approached, an insulated electric ignitor exteriorly positioned on said burner tube, electric conduit means connected thereto to deliver current to said ignitor and an ignitor shield on the burner tube below the insulated ignitor.

7. A bottom hole burner for initiating combustion in subterranean formations which comprises a gas intake chamber closed at the upper end and having closure means at the lower end, the upper end of said chamber including means for raising and lowering said chamber in well tubing, the lower end of said chamber being tapered to fit a shoulder in the lower end of the well tubing, said tapered end including seal means to prevent combustible gas flow out of the tapered end of the well tubing, a plurality of gas entry ports in said chamber adapted to receive combustion gas delivered down the well tubing, a vertically adjustable single bore nozzle in the closure means of said chamber communicating with the interior of said chamber through said closure means, a plurality of support arms fixed to the lower end of said chamber, an ejector supported by said arms below the nozzle adapted to receive air from the annulus between the well bore and the well tubing and gas issuing from said nozzle, an elongated burner tube permanently fixed to the lower end of said ejector in fluid tight communication therewith, said burner tube being closed at the lower end and having a plurality of perforations throughout its length, said perforations increasing in number per unit length as the closed end of the burner tube is approached, an insulated electric ignitor exteriorly positioned on the said burner tube, electric conduit means connected to said ignitor, said electric conduits being different metals and connected in the vicinity of the ignitor to provide a thermocouple.

8. A bottom hole burner for initiating combustion in subterranean formations which comprises a gas intake chamber closed at the upper end, the upper end of said chamber including means for raising and lowering said chamber in well tubing, said lower end of the chamber being tapered to fit a shoulder in the lower end of the well tubing, said tapered end including seal means to prevent combustible gas flow out of the end of the well tubing, a plurality of gas entry ports in said chamber adapted to receive combustion gas from the Well tubing,

a vertically adjustable single bore nozzle in the bottom of said chamber communicating with the interior of said chamber, a plurality of support arms fixed to the lower end of said chamber, an ejector supported by said arms below the nozzle adapted to receive air from the annulus between the well bore and well tubing, an elongated burner tube permanently fixed to the lower end of said ejector, said burner tube being closed at the lower end and having a plurality of perforations throughout its length, said perforations increasing in number per unit length as the closed end of the burner tube is approached, a plurality of exteriorly positioned ignitors on said burner tube, conduit means connecting said ignitors to the surface by means of which the ignitor can be activated from the surface.

9. A bottom hole burner for initiating combustion in subterranean formations which comprises a gas intake chamber closed at the upper end and having closure means at the lower end, the upper end of said chamber including means for raising and lowering said chamber in well tubing, said lower end of the chamber being tapered to fit a shoulder in the lower end of the well tubing, said tapered end including seal means to prevent combustible gas flow out of the end of the well tubing, a plurality of gas entry ports in said chamber adapted to receive combustion gas from the well tubing, a vertically adjustable single bore nozzle in the closure means of said chamber communicating with the interior of said chamber, a plurality of support arms fixed to the lower end of said chamber, an ejector supported by said arms below and adjacent to the nozzle adapted to receive air from the annulus between the well bore and well tubing and gas issuing from said nozzle, an elongated burner tube permanently fixed to the lower end of said ejector, said burner tube being open at the upper end and closed at the lower end and having a plurality of perforations throughout its length, said perforations increasing in number per unit length as the closed end of the burner tube is approached, a perforated bafiie tube surrounding said burner tube, an electric ignitor exteriorly positioned on the said burner tube, conduit means connecting said ignitor to the surface to means which provide activation of said ignitor.

References Cited in the file of this patent UNITED STATES PATENTS 951,060 Driesche Mar. 1, 1910 1,548,447 Dice Aug. 4, 1925 2,584,606 Merriam et al. Feb. 5, 1952 2,604,935 Ross July 29, 1952 2,636,445 Tutton Apr. 28, 1953 2,997,105 Campion et a1. Aug. 22, 196-1 August 21, 1962 Patent No. 3,050,123

J. 0. Scott ears in the above numbered patrtified that error app Patent should read as It is hereby ce tion and that the said Letters ent requiring correc corrected below.

Column 3, line 32, for "diamter read diameter line 51, for "igniter" read ignitor column 4L line 45,

line 55, for "445" read after "diverged" insert to Signed and sealed this 1st day of January 1963.,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Commissioner of Patents Attesting Officer 

